The leaked goodness comes from Videocardz, which reports that the Titan Z is a triple-slot card - but air-cooled. This is compared to the liquid cooler on the Radeon R9 295X2, which requires mounting in your case. There's dual 8-pin PCIe power, so we're looking at a total TDP of 375W on NVIDIA's dual GK110 product. But what about performance? The Titan Z doesn't beat the R9 295X2 in everything, but it comes close. When compared to GTX 780s in SLI, the Titan Z loses, with a much bigger gap.

The problem here is, even if it comes close to the R9 295X2, but doesn't beat it - the Titan Z is at least $3000 (without taxes). You can go and buy a SAPPHIRE R9 295X2 on Amazon for $1536 - half the cost of the Titan Z.

It looks like AMD's path of using an all-in-one liquid cooler was a good choice, as the temperatures on the Radeon R9 295X2 are quite a bit lower than the air-cooled Titan Z.